Safety device for nose fuze



United States Patent O 3,472,167 SAFETY DEVICE FOR NOSE FUZE Georg Henry Sixten Holmstrom, Karlstad, Sweden, as-

signor to Forsvarets Fabriksverk, Eskilstuna, Sweden, an agency of the Department of Defense of the Kingdom of Sweden Filed Dec. 15, 1967, Ser. No. 691,022 Claims priority, applicatzit/)g'lswedem Jan. 2, 1967,

Int. Cl. F42c 1/14 U.S. Cl. 102-73 2 Claims ABSTRACT OF THE DISCLOSURE A nose fuze having a detonating cap protruding out of the fuze body. The cap is protected by a hood which is arranged to be thrown off after having been removed from the fuze body. The removal is blocked by a locking device, which is unlocked by acceleration of the fuze. An outer protective hood that is manually removable, prevents the inner hood from being displaced and the locking device resumes its blocking condition, should it have accidentally locked up, such as by a projectile being dropped.

A fuze which is ar-med by acceleration forces acting on it can, under certain circumstances, be ignited by other acceleration forces than those which arise in the weapon. Consideration must be paid to this fact especially with rocket ammunition since the fuzes in such cases must be designed so as to be armed at comparatively small acceleration forces. The risk of accidental ignition is especially great in connection with loading from and to vessels since free fall from considerable height might occur. It is therefore not easy to base the safety device on differences in the extent of acceleration.

The present invention has for its object another and more effective solution to the problem of safe handling, and refers principally to a type of nose fuze provided with a device for bore safety, and which type of fuze is described in United States Patent No. 3,190,222. Such safety device comprises a detonating cap in the forward end of the fuze, a supporting bushing concentric to the fuze body and supporting the detonating cap, and a holding sleeve connected with a protective hood around the detonating cap, which sleeve is displaceable forwardly by means of inertia and spring power.

The protective hood is arranged to be moved out of safety position by being displaced forwardly. The safety device also comprises a locking device having one or more locking elements for keeping the holding sleeve in a rear position in the fuze body, and a blocking sleeve being arranged between the holding sleeve and the fuze body and being concentric to the same, which blocking sleeve, when the fuze is in an acceleration-free condition, bears against a rim inside of the fuze body and prevents the locking elements from being moved forwardly, but is released from its blocking position `so that the locking elements are brought aside at the acceleration of the fuze.

A fuze constructed according to the present invention includes 'an advancing spring for the blocking sleeve, a friction spring embracing the rear end of an annular means that is displaceable forwardly, taking along with it the locking elements, when these elements are released by the blocking sleeve during the acceleration period of the fuze, but which otherwise is blocked by the locking elements, whereby the blocking sleeve engages the friction spring, so that the spring, together with the annular means embraced by the spring and the locking elements, is advanced so far that the locking elements cannot be passed and blocked by the blocking sleeve. The fuze also com- Patented Oct. 14, 1969 "ice prises an outer protective hood which is arranged around the nose of the fuze but is manually removable, being fixed on the outside of the fuze body and bearing against the front side of the protective hood so that this inner hood and the holding sleeve are prevented from being displaced and thus prevent the locking elements from being advanced where they cannot be blocked once more by the blocking sleeve, when taking along with it the friction spring that the sleeve has returned to its forward position. By using a comparatively strong return spring for the blocking sleeve, the sleeve is pressed forwardly when the acceleration ceases, passing and reblocking the locking elements which keep the holding sleeve retained in its rear position. By arranging the friction spring around this sleeve, or another removable means actuating the locking elements, in such a way that this means and the locking elements are taken along with the spring Vand thereby with the blocking sleeve in its advancing position, it is impossible -for the latter to overtake and reblock these elements. Due to the fact that the outer protective hood bears against the inner protective hood, the latter and its holding sleeve are prevented from being displaced. This implies that the blocking sleeve, as a consequence of `an irrelevant acceleration, if it is moved rearwardly, will return to its blocking position since the friction spring will move along with the blocking sleeve without being able to take the removable means along with it and around which it is arranged.

When a projectile provided with 'a fuze is fired in a Weapon there is, however, nothing to prevent the friction spring from taking this means along with it since the outer protective hood has been taken ott before the ammunition is entered into the bore of the weapon. Also, the holding sleeve and another telescoping means around which the friction spring is arranged and which is blocked by the locking elements, as well as these locking elements themselves, are prevented from being displaced forwardly.

In the accompanying -drawing the figure shown consists of a longitudinal section of a -fuze having a safety device constructed according to the present invention.

The carrying part of the fuze includes a fuze body 7 having a bottom screw plug 31 and an outer hood composed of the elements 1, 2 and 3. The hood consists of a thick outer casing 2 of rubber or plastic and has a lining in the form of a thin metal casing 3 and in its nose, an inner protective body 1. The protective hood is an essential part of the device for insuring the requirements of safety handling and it also serves as a protective packing. In the extreme front part of the fuze body is an annular detonating cap 5, the same comprising a primer charge and an auxiliary charge 6 as well as a fastening part 10. In the rear end of the fuze body is arranged a booster that is composed of two parts 14 and 25 respectively and which contain charges 15 and 26 respectively. The front part `14 of the booster has a thick end wall 9 composed of metal and is so dimensioned that it can be entered intothe annular detonating cap 5.

The detonating cap 5 is fastened in the front end 11 of the supporting bushing 13 and the rear part 24 of the booster is carried within the rear end of the supporting bushing and is actuated by an advancing spring 27 that is placed between the booster part 25 and the supporting bushing 30. The two parts 15 and 26 of the booster are connected by means of a connecting sleeve 22, the outside of which forms a principally conical shoulder 21.

The detonating cap 5, the booster 15, 26 and the supporting bushing 30 together constitute with the blocking device, a so-called booster safety device, whereby the supporting bushing 30 forms a bearing housing for this device. The blocking device includes two diametrically placed locking balls 20, a blocking sleeve 19 having an inwardly directed flange 18 and a connecting sleeve 22. When the fuze is set at safety, the locking balls 20 are',l in a jam between the shoulder 21 of the sleeve 22 and the flange .18 of the blocking sleeve 19 which bea'" against a ledge 16 on the inner side of the fuze body. The supporting bushing 30 is provided with longitudinal slots 13, which allows the balls 20 to be displaced forwardly but the rear wall ends of which bear against the balls, so that the supporting bushing 30 is prevented from being displaced forwardly as long as the balls are in a locking position.

The fuze includes an inner protective hood 4 around the detonating cap 5. It is carried by a holding sleeve 12 around the supporting bushing 30 and is connected to said sleeve by means of a lock 8 which is not lockable within the fuze body 7 but prevents the protective hood 4 from being automaticaly separated outside of the fuze body. The inner protective hood 4 is prevented from moving forwardly by the outer protective hood composed of ythe elements 1, 2 and 3, by the hood 4 being in contact, or almost in contact, with the front end of the inner protective hood. The holding sleeve 12 is provided with a hole 17 for the locking balls 20, on its rear end.

The blocking sleeve 19 with its inwardly-directed ange 18, prevents the balls 20 from moving forwardly. Inside of the blocking sleeve is a friction spring 23 which presses against the supporting bushing 30. The rear end of the supporting bushing forms a flange 32, the -front rim 29 of which serves as a stopping means which, by stopping against a supporting ring 24, arranged behind the blocking sleeve 19, confines the forward motion of the supporting bushing 30 and designates `the return spring of the blocking sleeve 19. i

The function of the fuze, when the outer protective hood 1, 2 and 3 has been removed is as follows: Owing to the acceleration of the fuze in the weapon bore, the booster 14 and 25, and in connection with the connecting sleeve 22 with its shoulder 21, will be displaced backwardly, whereby its flange 18 presses the balls 20 inwardly against the connection sleeve 22 above its shoulder 21. When during the period of `decreasing acceleration of the fuze by the action of the spring 28, the blocking sleeve 19 moves forwardly again, it takes the friction spring 23 along with it, the spring in its turn taking the supporting bushing with it and which is removable a short distance. In its turn, the bushing takes the balls 20 along with it to a position so far ahead that the balls cannot be passed and reblocked by the flange 18 of the blocking sleeve 19, when the latter, taking the friction spring along with it, returns to its initial position.

When the booster 14, 25 moves forwardly by the action of the spring 27, it moves the balls 20 along the slot 13 in the supporting bushing 30. As they are in engagement with the holding sleeve 12, this sleeve is simultaneously moved forwardly and when the lock 8 reaches beyond the front rim of the front end of the fuze body 7, the inner protective hood 4 is thrown olf. In this position the booster 14, 25 with its end wall 9 is so far entered into the detonating cap that ignition can be transferred between them.

If the outer protective hood has not been removed, this fact will result in changed conditions for the function of the fuze. Thus, the inner protective hood 4 and also the holding sleeve 12 and the supporting bushing 30, will be prevented from being removed forwardly. This causes a changed function of the blocking device. After the blocking sleeve 19 has been moved backwardly, the fuze being subjected to an acceleration force, and when this force again decreases, the sleeve is forced forwardly by the return spring 28, taking with it the friction spring 23, which however, cannot take the supporting bushing 30' with it but slides on its outer side. The locking balls 20 are therefore in their rear position, but are still removable, since the connecting sleeve 22 and its shoulder 21 have not returned to their initial position in time and are therefore passed by the flange 18 of the blocking sleeve, which thereby takes its original blocking position.

The described fuze comprises not only a detonating cap safety device in the shape of a protective hood, but also a booster safety device, that is, a safety device which blocks the transfer of ignition from the detonating cap to the booster. The present invention does not require that such a booster safety device be an integral part of the fuze. There must however, be some means which takes o-ver the task of the connecting sleeve 22 to assist in blocking the locking balls 20 when the fuze is in acceleration-free condition and in conjunction to block the forward motion of the blocking sleeve 19. The holding sleeve 12 must be loaded by an advancing spring, either directly or by a means corresponding to the connecting sleeve 22, which means presses the locking balls 20 forwardly, said balls taking the holding sleeve 12 along with them.

The holding sleeve can also reach farther back than iS shown in the drawing, and the friction spring 33 can be arranged around the sleeve on its rear end instead around the supporting bushing 30.

What is claimed is:

1. A safety device for a nose fuze comprising, a hollow fuze body, a supporting bushing with a detonating cap in the. forward end of said body, a holding sleeve co-axial with the bushing, an inner protective hood connected to said sleeve, said bushing being displaced forwardly by means of inertia and spring power, locking elements for keeping the holding sleeve down in the fuze body, a blocking sleeve located between the fuze body and the holding sleeve, an inwardly directed stop shoulder in the fuze body against which the holding sleeve abuts when the fuze iS not under acceleration thus preventing forward movement of the locking elements, a friction spring disposed around the rear end of the Supporting bushing, a spring-loaded gui-ding ring pushing the friction spring and supporting bushing forwardly, said holding sleeve being removable forwardly after a launch but being blocked by the locking elements when the fuze is not under acceleration, an outer protective hood attached to the forward end of the fuze body, said hood abutting against a leading end of the inner protective hood preventing the latter hood, sleeve and locking elements from moving forwardly.

2. A safety device according to claim 1 wherein the supporting bushing for the detonating cap is kept down by the locking elements and the holding sleeve when the fuze is not under acceleration, said supporting bushing being displaceable with said holding sleeve during periods of decreasing acceleration only when said outer protective hood has first been removed from said fuze, and wherein said supporting bushing projects rearwardly of said holding sleeve and said friction spring is tted to the rear end of said holding sleeve.

References Cited UNITED STATES PATENTS 2,456,289 12/1948 Lindman 102--76 X 2,496,351 5/1949 Lauritsen 102-76 3,190,222 6/1965 Holmstrom 102-73 BENJAMIN A. BORCHELT, Primary Examiner I. FOX, Assistant Examiner 

